1. Field of the Invention
This invention relates to electrosurgical devices and more specifically to bipolar blood coagulation apparatus and method for arthroscopy.
2. State of the Prior Art
Arthroscopic surgery is used to treat: (i) torn menisci, anterior cruciate, posterior cruciate, patella malalignment, synovial diseases, loose bodies, osteal defects, osteophytes, and damaged articular cartilage (chondromalacia) of the knee; (ii) synovial disorders, labial tears, loose bodies, rotator cuff tears, anterior impingement and degenerative joint disease of the acromioclavicular joint and diseased articular cartilage of the shoulder joint; (iii) synovial disorders, loose bodies, osteophytes, and diseased articular cartilage of the elbow joint; (iv) synovial disorder, loose bodies, ligament tears and diseased articular cartilage of the wrist; (v) synovial disorders, loose bodies, labrum tears and diseased articular cartilage in the hip; and (vi) synovial disorders, loose bodies, osteophytes, fractures, and diseased articular cartilage in the ankle. When performing an arthroscopy of the shoulder, elbow, wrist, hip, knee, or ankle involving connective tissue using a rotary shaver, the laceration of blood vessels, such as veins and venuals, arterials and arteries, and capillaries, produces bleeding. Very minor bleeding can be tolerated if the sterile fluid used in arthroscopy flushes the blood away and maintains visibility in the joint. However, if a damaged blood vessel bleeds enough to impair the surgeon's vision in the joint, the bleeding has to be stopped quickly and efficiently to avoid delays or possibly even having to abort the arthroscopic procedure. While it is not desirable, bleeding can be controlled in a knee joint by applying a tourniquet to the thigh above the knee. However, no tourniquet is possible to stop bleeding in the shoulder, and some surgeons would prefer not to use tourniquets in arthroscopy of other joints, such as elbows, wrists, hips, knees, and ankles, if bleeding can be controlled in other ways. Also, excessive bleeding can cause the surgeon to have to provide a temporary drain in the joint for post surgery draining of excessive blood accumulation in the joint.
The most common method of controlling bleeding blood vessels, "bleeders," in arthroscopic procedures in shoulders and in other joints when tourniquets are not possible or desirable is to use a monopolar electrosurgical probe to coagulate or cauterize the bleeding blood vessel. A typical monopolar electrosurgical device utilizes a monopolar probe for one electric pole and a large area plate in contact with the patent's skin at a location remote from the arthroscopic surgery, such as the patient's back, for the other electric pole. Both the probe and the plate are connected electrically to a radio frequency (RF) generator. When the tip of the monopolar probe is positioned adjacent or touching the connective tissue and the RF electrical power is turned on, the person's body completes the electric circuit between the monopolar probe and the large area plate, and electric current flows through the patient's body between the monopolar probe and the plate. When enough current and voltage is applied, the tissue where the current is flowing will get hot and result in hemostasis (stopping the flow of blood) and necrosis (pathologic death of cells) of the surrounding tissue. Since the plate is in contact with a much larger surface area of the body than the monopolar probe, the density or concentration of the electric current flowing through the body tissue is greater at the probe than at the plate. Therefore, the tissue adjacent the monopolar probe becomes hotter than the tissue adjacent the plate, and the heat produced where the monopolar probe contacts the tissue where the bleeding occurs causes coagulation resulting in hemostasis (stemming flow of blood). In addition, normal tissue adjacent the probe contact point becomes denatured and damaged by the heat produced by electric current flowing through the tissue near the probe during this coagulation method. Therefore, when the monopolar probe is positioned on the tissue surrounding the bleeder, or on the bleeding blood vessel itself, the RF current will cause denaturing and necrosis at the target site as well as of the surrounding tissue. Since the electric current flows through the body tissue between the monopolar probe and the remotely located plate, the depth and volume of necrosis is indefinite and difficult to control, but can easily extend, for example, to over one centimeter wide and over one-half centimeter deep in a typical operation to stop a bleeder, but it will continue to extend even deeper as long as the monopolar probe is held in contact with the tissue while the power is turned on. While such monopolar coagulation is effective to stop the bleeding, it also denatures a considerable amount of surrounding tissue, thus necrosing more of the normal surrounding connective tissue in the joint than is strictly needed or desired.
The bipolar coagulator disclosed in U.S. Pat. No. 5,089,002, issued in 1992 to Lawrence T. Kirwan, Jr., one of the co-inventors of this invention, and which is incorporated herein by reference, is a bipolar device that was designed for desiccating several microscopic layers of eye tissue, including tiny blood vessels, on the eye before eye surgery in order to reduce bleeding encounters during eye surgery. The result is that the tiny blood vessels near the eye surface, where the surgical incisions are to be made during eye surgery, are necrosed--virtually obliterated or erased--before any incisions are made. A bipolar coagulator similar to that shown and described in U.S. Pat. No. 5,089,002, but with an electrical insulation coating around substantially the entire length of the outer conductor or electrode, was also developed by Lawrence T. Kirwan, Jr., for very fine hemotosis in neural endoscopy applications where the insulation coating prevents outer electrode contact with surrounding tissue. However, both of those bipolar coagulators developed by Kirwan are designed for the specific eye surgery and neural endoscopy necrosing applications described above, which are not in fluid-filled environments and which are not effective for coagulating bleeders encountered in the arthroscopy procedures described above.